It has been found desirable in heat exchangers, particularly those used for condensers in refrigerator systems, to utilize a serpentine tube configuration. The tubes are flat and are bent to form a plurality of straight runs connected by U-shaped bends whereafter fins or air centers are inserted into the spaces between opposed runs of the tube structure. The tubes thus act as a passageway for the refrigerant and the fins increase the heat transfer capacity of the heat exchanger.
The assembly of the fins between the runs of the tube structure, without special methods and equipment, would be a difficult and time consuming process requiring hand insertion of the fins one at a time. Further, once the fins are assembled into the core they must not move during subsequent handling or brazing. Steel banding straps are typically used to hold the core together until brazing is completed. However, the banding pressures are not transmitted uniformly throughout the entire core. Specifically, the portions of the tube proximate the bends are relatively stiff and resist the externally applied pressure so that the fins in such areas would be loosely held at best. It has been proposed, in U.S. Pat. No. 4,942,654 assigned to the assignee of the present application, to facilitate the insertion of the fins into the spaces between the tube runs by utilizing a special tooling to spread the tube runs slightly whereafter the fins are easily inserted into the spaces between the tube runs whereafter the tube spreaders are removed and the tubes spring back to their original spacing to hold the centers tightly in place. While the method and apparatus of U.S. Pat. No. 4,942,654 have facilitated the heat exchanger assembly process, insertion of the fins into the spaces is still a time consuming process and there is still a danger that the delicate fins may be damaged during this insertion process.